MyKell

When you clone a human being, you don't get an "exact copy" of him/her. Insteadyou get someone who is more like an identical twin (depending of course where you take the ovum from, and how much mitochondrial DNA affects our traits)
So, I was thinking about this issue. In particular, I was thinking whether the brain wiring during development is never identical in identical twins because
1. The environment is different... There is no way that both environments can be the same, even in utero, or
2. That wiring of the brain, and synaptogenesis is ultimately operated by protein-protein, protein-lipid, salt, etc... interactions, which are bound by the uncertainity principle.

The question is: Is the brain, and for that matter, a biological system, better described as a classical or a quantum system? Is a cellular response ever affected by the uncertainity principle?

Undercurrent

Roger Penrose notwithstanding, I don't think that there's any particular reason that biological systems need to be described by quantum mechanics, other than through the standard intermediate approximations of classical physics and chemistry. Tissues, cells, and organelles are all much bigger than the "usual" quantum systems.

MyKell

what about protein-protein interactions.. or Macromolecular interactions in general. Are those classical or quantum?

Undercurrent

Of course, at some point it's a false dichotomy. Everything is described by QM at some level, and qunatum effects come into play gradually with size, rather than coming into effect all at once.

But everything I've seen regarding the interactions of macromolecules in biological systems seems to treat them effectively as "structures" with a charge distrubution over their surface, and perhaps some articulation points, and this approximation is adequate for understanding the properties of the molecule. The only real entrance of QM into the discussion is through the electronic properties of the constituent atoms, which give rise to the charge distirbution, but simply knowing a few facts about how the charge distribution of specific atoms would give a pretty good approximation even with a "ball-and-stick" molecular model.

I'd consider entaglement to be the gold standard of when a system "has" to be described by QM if it is going to be described at all, and I have yet to see any case where entaglement is exploted in the description of a biological system. Penrose argues that it is exploited in a human brain, but not very convincingly.